This invention relates generally to apparatus and methods for supporting and guiding an elongated flexible member between relatively movable termination points, such as, for example, a flexible cable connected between points on a stationary frame and a component movable with respect to the frame. More particularly, this invention relates to a mounting assembly designed for supporting and guiding an elongated flexible member such as a cable throughout relatively rapid movements including directional changes and related accelerations with minimal mechanical stresses or frictional wear to ensure long term reliability.
In the past, many different mechanical and electromechanical devices have included relatively movable components requiring some type of elongated flexible member such as a cable or like interconnection between the components. For example, many such devices have required an electrical conductor cable to be connected between relatively movable structures for purposes of supplying electrical power and/or a variety of electrical control signals. Other such devices have required pneumatic or hydraulic tubing connections or other types of flexible connections between, for example, a main stationary frame and a movable component of a machine. In each instance, the flexible interconnection must be designed to supply the movable component with the appropriate electrical signal, fluid, or similar input while exhibiting sufficient flexibility to accommodate the direction, range, and speed of motion of the movable component. However, when the movable component is designed for relatively rapid and/or multidirectional movements, particularly with frequent and rapid accelerations and decelerations, available flexible connectors have not provided satisfactory fatigue life and resistance to mechanical wear.
More particularly, by way of one specific example, video cassette storage and playback systems have been proposed for use by television broadcast stations for automated transfer of video cassettes between a storage library and playback equipment, thereby permitting automated or semi-automated station operation with selected prerecorded programs or commercial messages being played according to a timed, preprogrammed sequence. In such systems, a mobile carriage including a cassette pick-up and release unit is transported by a multidirectional transfer mechanism back and forth, for example, within a X-Y plane, between the storage library and the playback equipment to select, transfer, play and return to the library selected cassettes. The pick-up unit includes appropriate movable components for engaging and releasing the cassettes in accordance with various commands communicated thereto via a multiple conductor flexible cable. However, when the system is designed for rapid displacements of the pick-up unit to meet the cassette changeover timing demands of a modern broadcast station, the flexible cable can be subjected to significant mechanical loads and/or sliding friction resulting in premature cable failure. This is particularly true in the event the cable is freely suspended between two relatively movable components, wherein high accelerations and decelerations create the relative movement which thrashes the cable about, resulting in cable damage.
In the past, a variety of flexible conductor cable designs have been proposed in attempts to increase cable life span while permitting sufficient freedom of cable motion to track the moving component or components. For example, spirally coiled conductor cables have been commonly used, but such cables tend to flap about when subjected to rapid accelerations and/or directional changes. Attempts to constrain a spirally coiled cable against flapping have met with little success due to increased frictional wear as the cable slides relative to the constraining apparatus. Other designs have utilized spring-loaded arrangements to apply a constant spring tension to a multiconductor flat ribbon cable throughout various cable movements, but these designs undesirably subject the cable to significant tension loads with resultant decrease in operating life. Still other proposals have envisioned threading a flat ribbon cable through a chain of pivoted links, but such links have tended to be relatively noisy during rapid displacements and further are not well-suited for accommodating cable motion along multiple axes.
In many hydraulic and pneumatic equipment applications, flexible tubing is frequently connected between two relatively movable components to convey fluid and/or pressure signals therebetween. In the past, such flexible tubing has typically been suspended freely between the movable components. However, when relatively high accelerations, decelerations and/or component transport speeds are required, freely suspended tubing will thrash about to slap against adjacent structures and apply high stress upon coupling members provided at the ends of the tubing, all resulting in early failures of the tubing and the coupling members.
There exists, therefore, a significant need for an improved apparatus and method for movably mounting and supporting an elongated flexible member connected between relatively movable components, wherein the mounting arrangement permits rapid movements and accelerations of the flexible member to accommodate positional changes of a moving component along one or more directions, and without subjecting the flexible member to significant mechanical loads or significant sliding friction. The present invention fulfills these needs and provides further related advantages.